Drug delivery systems are available in a great variety of shapes and forms, among the most common of which are coated compressed hard tablets, caplets and filled gelatin capsules. The use of gelatin capsules for the encapsulation of medicinal agents has been a popular method for administering drugs because many patients prefer to swallow capsules and caplets rather than tablets.
Caplets are solid, oblong tablets which, although very popular as a drug delivery vehicle, have not reached the same level of consumer acceptance gelatin capsules once had. To solve this problem, the pharmaceutical industry has sought to combine the consumer acceptance of a capsule shape with a caplet. U.S. Pat. No. 4,820,524 relates to a caplet with a two color gelatinous coating to produce a shiny, capsule-like medicament. The disclosed process produces the capsule-like medicaments by individually dipping and drying first one end of each caplet into a first bath of gelatinous coating of one color, and then the other end of each caplet into a second bath of gelatinous coating of a different color. The production of these capsule-like medicaments is reported to be readily facilitated by modifications to existing empty gelatin capsule making equipment. This process of separate dippings to achieve the simulated capsule-like medicament, however, hinders production of these medicaments because it requires an extra dipping and drying step for coating the gelatin onto the caplet.
U.S. Pat. No. 4,591,500 relates to a tablet having the exact shape of a gelatin capsule compressed along the longitudinal or axial direction to form a single transverse ledge at its mid-section instead of extending along the longitudinal axis as in conventional tableting machines, which compress the tablets in the transverse direction. The apparatus disclosed for producing the capsule-shaped tablets consists of a molding device provided with an upper punch and a lower punch of differing longitudinal and lateral dimensions, which creates a ledge or land area where the upper and lower punches come together. A problem inherent in the production of the disclosed tablet by the disclosed apparatus, however, is that the ledge or land area must be at the center of each tablet. This can only be accomplished by compressing the raw materials at the same point in the die to produce each tablet. This is a critical consideration for the production of this product. Further, this reference does not contemplate production of a capsule-type product, i.e., a two colored bi-layer capsule-shaped tablet covered with a coating.
Canadian Patent 1,223,209 relates to a caplet having a capsule shape which is covered with a film coating to simulate both the appearance and function of a gelatin capsule medicament. The disclosed caplet has a body and cap portion in which the outside diameter of the cap portion is greater than the outside diameter of the body portion. The disclosed process produces this shape by compressing powdered material in an appropriately shaped die between appropriately shaped upper and lower punches. The reference advises that the punch edges of the upper and lower tablet punches not be allowed to come in contact with each other during the compression process because this would tend to destroy the punches. A consequence of the procedure, however, is that it forms a seam around the longitudinal equator of the caplet. Therefore, rather than disclosing a medicament with a true capsule shape, the reference discloses a caplet possessing the ledge or step of a capsule, but not the two color appearance of a capsule, nor the cylindrical shape of a capsule.
U.S. Pat. No. 3,158,109 relates to a multi-layer tablet making machine for producing compressed tablets composed of two or more superimposed layers. This patent discloses machines comprising a plurality of dies, each of which successively receives a plurality of powder fills. These first fills are individually precompressed prior to the successive fills entering the die. This precompression of the individual fills reportedly insures a clear delineation between the individual layers in the finished tablets which is clearly visible where powders of different colors are employed for successive fills. This process of making multi-layer tablets discloses compression of the tablets along the smaller dimension of the conventional tablet shapes which are typically made of two different materials.